1. Field of the Invention
The present invention relates to a magnetic head device having a plurality of recording head elements, and a rotary head device using the same, a magnetic tape device, a magnetic disc device and a magnetic recording method.
This application claims priority of Japanese Patent Application No. 2004-090322, filed on Mar. 25, 2004, the entirety of which is incorporated by reference herein.
2. Description of Related Art
Generally, a magnetic head supplies a current corresponding to a recording signal to a coil. A magnetic flux flows to a pair of magnetic cores by a magnetic field generated from this coil, and a recording magnetic field is generated in a magnetic gap between the magnetic cores. The magnetic head records the signal by applying the recording magnetic field to a magnetic recording medium. Heretofore, as such a magnetic head, so-called a bulk type magnetic head, in which a pair of magnetic cores made of a magnetic material are opposed to form a magnetic path, a magnetic gap of an minute space is formed on the opposed surfaces of the pair of the magnetic cores, and a coil for generating the magnetic field is wound around the magnetic cores, is used. Further, so-called a metal in gap (MIG) type magnetic head, in which in association with recently a high recording density, metal magnetic thin films having a high saturation magnetic flux density are formed on the opposed surfaces of a pair of magnetic cores made of a ferrite, etc. and these metal magnetic thin films are opposed via a non-magnetic film or a magnetic gap, has been in practical use.
However, in such a magnetic head, to respond to a request for raising a recording density, a track width is narrowed, and the improvement in the dimensional accuracy in the track width direction becomes important more and more. However, there is a limit to manufacture the magnetic head by finely processing it, and it becomes very difficult to narrow the track width in response to the high recording density.
Therefore, as the magnetic head corresponding to the high recording density, so-called a thin film magnetic head, in which respective constituting elements are laminated on a substrate by a thin film forming technique, is proposed. Since the constituting elements of the magnetic core, coil, etc. in this thin film magnetic head are formed by a thin film forming technique such as a plating method, a sputtering method, an ion milling method, etc., a dimensional miniaturization, such as track narrowing, gap narrowing is facilitated, a size is reduced, and a recording density on a magnetic recording medium can be raised.
For example, in a thin film magnetic head 400 shown in FIG. 1, FIG. 2 and FIG. 3, a lower magnetic core layer 402 and an upper magnetic core layer 403 for forming a magnetic path are laminated on a substrate 401. The lower magnetic core layer 402 and the upper magnetic core layer 403 respectively have protruding parts 402a and 403a protruding from the ends of the opposed surface 400a side, opposed to the magnetic recording medium by predetermined track width sizes w2′, w1′. These protruding parts 402a and 403a are opposed to each other via a non-magnetic layer 404 to form a magnetic gap G′. The lower magnetic core layer 402 and the upper magnetic core layer 403 are connected at the other end separated in a depth direction from the opposed surface 400a to form a back gap. A thin film coil 405 wound spirally at this back gap as a center is provided to be embedded in the non-magnetic layer 404. The ends of an inner peripheral side and an outer peripheral side of the thin film coil 405 are extended toward the opposite side to the opposed surface 400a. Here, external connection terminals 405a, 405b connected to an external circuit are provided. A protective layer 406 covering the entire surface except the parts that the external connection terminals 405a, 405b of the thin film coil 405 face outside is provided on the uppermost layer of this substrate 401.
In the thin film magnetic head 400 as described above, respective constituting components are formed on the substrate 401 by the thin film forming technique, and hence the track can be narrowed, and the request for further raising the recording density of the magnetic recording medium can be responded. It is proposed that the thin film magnetic head 400 manufactured by such a thin film manufacturing process is utilized for a magnetic disc device, such as a hard disc drive (HDD), etc. at an the beginning, and is utilized recently for a magnetic tape device, such as a video tape recorder (VTR), a tape streamer, etc.
Incidentally, in the above-mentioned thin film magnetic head 400, it is general that the track width size w2′ of the lower magnetic core layer 402 formed on the substrate 401 is larger than the track width size w1′ of the upper magnetic core layer 403 formed thereon.
More particularly, in the above-mentioned thin film manufacturing process, as shown, for example, in FIG. 4, it is easy to form a layer 501 having a wide width on a substrate 500 and to form a layer 502 having a narrow width thereon. On the other hand, as shown in FIG. 5, if the layer 501 having a wide width is formed on the layer 502 having a narrow width, since both the ends of the layer 501 having a wide width in the width direction cover both the ends of the layer 502 having a narrow width, the layer 501 having a wide width becomes a round shape. In this case, it is difficult to form the layer 501 having a wide width in a desired shape, such as, for example, linearly long in a width direction.
Therefore, in order to solve such a problem, as shown in FIG. 6, it is necessary to adopt special steps of forming layers 503 having the same thickness at both sides of the layer 502 having a narrow width and forming the layer 501 having a wide width thereon.
However, even if such steps are adopted, it is not easy to form the layers 503 having the same thickness at both sides of the layer 502 having a narrow width. For example, as shown in FIG. 7, if the layers 503 being thinner than the layer 502 are formed at both sides of the layer 502 having a narrow width, the layer 501 having a wide width and formed thereon becomes the shape in which both the ends of its width direction are bent downward. On the contrary, if the layers 503 being thicker than the layer 502 are formed, the layer 501 having a wide width and formed thereon becomes the shape in which both the ends of its width direction are bent upward. Further, as shown in FIG. 8, a gap 504 might be formed between the layer 502 having a narrow width and the layers 503 formed at both the ends of its width direction. Even in this case, it is difficult to form the layer 501 having a wide width in a desired shape.
Therefore, even in the above-mentioned thin film magnetic head 400, the track width size w2′ of the lower magnetic core layer 402 formed on the substrate 401 becomes larger than the track width size w1′ of the upper magnetic core layer 403.
Here, in the thin film magnetic head 400 formed by the above-mentioned thin film manufacturing process, when a recording magnetic field is excited in the magnetic gap, a magnetic saturation occurs at the upper magnetic core layer 403 side before the lower magnetic core layer 402 side. More particularly, the magnetic saturation occurs on the way of reaching the opposed surface of the gap in the protruding part 403a disposed at the distal end of the upper magnetic core layer 403, and as its magnetomotive force increases, this magnetic saturation region is moved toward the gap opposed surface. In the thin film magnetic head 400, there occurs an inconvenience that, when the magnetic saturation becomes large on this gap opposed surface, the gradient of the recording magnetic field leaked from the magnetic gap is lowered (for example, refer to Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 6-28628).
Therefore, in Patent Document 1, it is proposed to prevent the gradient of the recording magnetic field leaked from the magnetic gap G′ from becoming small by driving the region that the magnetic saturation occurs first when the magnetomotive force is raised on the way arriving from the distal end of the upper magnetic core layer 403 at the gap opposed surface by broadening the gap length of the thin film magnetic head 400 wider than the minimum recording magnetizing bit length.
On the other hand, in an HDD using this thin film magnetic head 400 as a recording head, as shown in FIG. 9 and FIG. 10, the thin film magnetic head 400 is placed on the rear end of the head slider 601 mounted at the distal end of a suspension 600, the thin film magnetic head 400 records a signal on a magnetic disc 602 while slightly the head slider 601 floats over the signal recording surface of the magnetic disc 602 rotating in a direction of arrows F in the drawings.
Here, the thin film magnetic head 400 is laminated in the order of the lower magnetic core layer 402, the non-magnetic layer 404 and the upper magnetic core layer 403 on the substrate finally becoming the head slider 601. The lower magnetic core layer 402 having a wide width is positioned at the preceding side (called a leading side) in the scanning direction of the head, and the upper magnetic core layer 403 having a narrow width is positioned at an opposite side (called a trailing side) to this leading side. Thus, in the thin film magnetic head 400, the recording bit normally recorded by the magnetic field generated from the upper magnetic core layer 402 of the leading side is rerecorded by the magnetic field generated from the upper magnetic core layer 403 of the trailing side to thereby form a recording track. Therefore, the track width of the recording track formed on the magnetic recording medium by this thin film magnetic head 400 strongly depends on the track width size w1′ of the upper magnetic core layer 403.
As described above, in the thin film magnetic head 400 which is formed by the thin film manufacturing process, if the track width is intended to be narrowed to respond to the request of raising the recording density, the track width size w1′ of the upper magnetic core layer 403 becoming narrower than the lower magnetic core layer 402 becomes more narrower.
However, if the track width size w1′ of the protruding part 403a disposed at the distal end of the upper magnetic core layer 403 becomes excessively narrow, a magnetic saturation occurs on the way of reaching the gap opposed surface so that a phenomenon occurs, in which the concentration of the magnetic flux at the magnetic gap G′ occurs and the magnetic flux is difficult to be distributed. In the thin film magnetic head 400, problems such as a reduction in the maximum recording magnetic field, a deterioration of a recording magnetic field distribution, a recording penetration due to a side fringing magnetic field, etc., occur. Further, problems such as a deterioration of an overwrite characteristics that is a characteristic in the case of overwriting, and a difficulty in a magnetic saturation operation of a high-frequency drive region.
More particularly, in this thin film magnetic head 400, as the track width size w1′ of the upper magnetic core layer 403 becomes narrow, demerits are rather increased than the merits for bringing about the magnetic saturation on the way of arriving at the gap opposed surface of the upper magnetic core layer 403 described in the above-described Patent Document 1 (for example, refer to Patent Document 2: Jpn. Pat. Appln. Laid-Open Publication No. 2000-251219).
Therefore, in Patent Document 2, it is proposed that the upper magnetic core layer 403 is divided into a magnetic pole layer becoming a magnetic pole part, one end side of which approaches to a medium opposed surface, a first yoke layer as a yoke part connected to the other end side of the magnetic pole layer and a second yoke layer. Further, the width at the end of the medium opposed surface side of the magnetic pole layer is smaller than the width at the end of the medium opposed surface side of the connecting part of this magnetic pole layer to the first yoke layer, and the width of the magnetic pole layer at the end of the medium opposed surface side of the connecting part of this magnetic pole layer to the first yoke layer is larger than the width of the first yoke layer at the end of the medium opposed surface side of the connecting part of this magnetic pole layer to the first yoke layer.
In this case, the magnetic saturation in the gap opposed surface of the upper magnetic core layer 403 can be brought about without bringing about the magnetic saturation on the way of arriving at the gap opposed surface of the upper magnetic core layer 403.
However, according to the method described in Patent Document 2, the magnetic saturation occurs on the gap opposed surface of the upper magnetic core layer 403, while the amount of a magnetic flux passing through the upper magnetic core layer 403 having a narrow width is reduced. In order to prevent this, it is necessary to hold the sectional area (track width×film thickness) of the upper magnetic core layer 403 at least at a predetermined value. That is, if the track width size w1′ of this upper magnetic core layer 403 is narrowed, the film thickness s1′ must be increased proportional to the reciprocal number of the track width size w1′.
Therefore, in the thin film magnetic head 400, as shown in FIG. 11, since the film thickness s1′ must be increased by the part narrowed of the track width size w1′ of the protruding part 403a disposed at the distal end of the upper magnetic core layer 403, in the thin film manufacturing process, the film forming time proportional to the film thickness of the upper magnetic core layer 403 is required. As a result, there occurs a problem that its manufacturing cost increases. Further, the larger the film thickness of the upper magnetic core layer 403 increases, the more the deterioration of the dimensional accuracy of the track width direction is caused. It becomes difficult to narrow the track width w1′ of the upper magnetic core layer 403 corresponding to the high recording density (for example, refer to Patent Document 3: Jpn. Pat. No. 2574260).
Therefore, in Patent Document 3, it is proposed that the track width accuracy of the upper magnetic core layer 403 is improved by forming the upper magnetic core layer 403 in a two-layer structure of a first magnetic layer formed in a predetermined track width size and a second magnetic layer formed in a narrower track width size than the first magnetic layer.
However, in the method described in Patent Document 3, the dimensional accuracy of the track width direction of the upper magnetic core layer 403 is improved, but a problem that a manufacturing cost is increased due to the increase in the film thickness s1′ of the above-mentioned upper magnetic core layer 403 cannot be solved.
Incidentally, as known references relating to the present invention, there are, for example, Patent Document 4: Jpn. Pat. Appln. Laid-Open Publication No. 2002-216313 and Patent Document 5: Jpn. Pat. Appln. Laid-Open Publication No. 2003-338012.
In these Patent Documents 4, 5, there is described a constitution that a plurality of recording head elements are sequentially laminated via insulating layers on a base by the above-mentioned thin film forming technique and the laminated recording head elements are deviated in a direction perpendicular to the laminating direction and disposed.